The invention relates to a fuel injection pump for an internal combustion engine having an adjusting piston effecting the adjustment of the instant of injection, first and second work chambers which are disposed on opposite ends of the adjusting piston and which communicate via respective first and second inflow lines with a pressure medium supply having a pressure which is varied in accordance with rpm, and a first control valve, which is disposed in either the first inflow line or an outflow line of the first work chamber, for controlling the first work chamber pressure.
In a known injection pump of this type, the outflow line contains not only a work chamber, which includes a restoring spring acting upon the adjusting piston, but also a control slide, which is displaceable by the rpm-dependent pressure of the pressure medium supply such that beyond a predetermined rpm, the control slide closes the outflow line of this work chamber; or, in an alternative realization, the control slide switches a throttle into the outflow line. This switching process is effected in addition to and independently from the first actuation, by means of an expanding-material element upon the attainment of the engine operating temperature. In this known embodiment, a throttle is disposed in the pressure medium inflow to the work chamber.
With this apparatus, the pressure is reduced only in the work chamber containing the restoring spring when the engine is cold and below a fixed final rpm. There are thus very few opportunities for taking into consideration other parameters in adjusting the instant of the injection.